The title for this application has been changed from "A Morphometric Analysis of Cochlear Tissues" to "The Role of the Stria Vascularis in Hearinb Dysfunctions." While the research emphasis has not changed, this new title more accurately described the research. The overall goal of this research is to provide a better understanding of the structure and function of the stria vascularis in order to determine its role in certain hearing dysfunctions. This goal will be reached using quantitative anatomical methods and by experimental manipulaton of the stria vascularis. The specific aims include determining the cell membrane surface area of strial cells and organelles, investigating the mechanisms involved in sound-induced alterations of the stria vascularis, investigating the mechanisms involved in alterations of the stria vascularis following ototoxic drug administration and comparing the structure/function relationships among the four primary components of the stria vascularis. This last specific aim is particularly important as it has the potential of providing fundamental information on the ion and fluid transporting properties of the stria vascularis. These studies have particular health relevance in the areas of noise- and drug-induced hearing loss and in Meniere's disease and endolymphatic hydrops. Although the cause of these diseases is unknown, data suggest a link between strial dysfunction and these diseases.